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191.
Understanding the nature and relative importance of various drivers of change is crucial for sustainable management of natural resources and in prioritizing management efforts, allocating limited resources, and understanding cumulative effects. For this article, we employed structured an expert judgments approach to identify, characterize, and assess the relative importance of the key biophysical and socioeconomic drivers of change within the Volta River Basin, West Africa. Precipitation variability, water availability, land use change, drought events, and population growth were perceived as most important, while biodiversity loss, social conflicts, pest and disease occurrence, urbanization, and pollution were viewed as less critical. A majority of these drivers were characterized as “slow” acting processes as compared to rapidly changing drivers. Intra- and interexpert groups agreement were found to be significant and convergent, indicating the reliability of the results. The implications of these results for sustainable water resources management and agricultural production are discussed. 相似文献
192.
James Forrest Ron Johnston Frank Siciliano David Manley Kelvyn Jones 《The Australian geographer》2017,48(4):457-472
Recent decades have seen substantial growth across many developed-world countries of right-wing populist political parties whose policies oppose immigration and multiculturalism as threats to the majority way of life there. These are exemplified in Australia by Pauline Hanson’s One Nation Party, which was successful at elections there at the turn of the twenty-first century and again in 2016. Part of this party’s rhetoric focuses on the geography of immigrant groups in Australia’s cities, with claims that their members live in ghettos. Is that factually correct? Using data from the 2011 Australian census this paper analyses the distribution of Asians and Muslims (the two groups picked out by One Nation and its leader) at four spatial scales within the country’s 11 largest urban areas. It finds no evidence at all of intensive residential segregation of Muslims, and although there are concentrations of Asians—notably in Sydney and Melbourne—most residents claiming Asian ancestry live in neighbourhoods and suburbs where they form a minority (in many cases a small minority) only of the local population. 相似文献
193.
The excitation of methanol in the absence of external radiation is analyzed, and LTE methods for probing interstellar gas considered. It is shown that rotation diagrams correctly estimate the gas kinetic temperature only if they are constructed using lines whose upper levels are located in the same K-ladders, such as the J0?J?1E lines at 157 GHz, the J1?J0E lines at 165 GHz, and the J2?J1E lines at 25 GHz. The gas density must be no less than 107 cm?3. Rotation diagrams constructed from lines with different K values for their upper levels (e.g., 2K?1K at 96 GHz, 3K?2K at 145 GHz, 5K?4K at 241 GHz) significantly underestimate the temperature, but enable estimation of the density. In addition, diagrams based on the 2K?1K lines can be used to estimate the methanol column density within a factor of about two to five. It is suggested that rotation diagrams should be used in the following manner. First, two rotation diagrams should be constructed, one from the lines at 96, 145, or 241 GHz, and another from the lines at 157, 165, or 25 GHz. The former diagram is used to estimate the gas density. If the density is about 107 cm?3 or higher, the latter diagram reproduces the temperature fairly well. If the density is around 106 cm?3, the temperature obtained from the latter diagram should be multiplied by a factor of 1.5–2. If the density is about 105 cm?3 or lower, then the latter diagram yields a temperature that is lower than the kinetic temperature by a factor of three or more, and should be used only as a lower limit for the kinetic temperature. The errors in the methanol column density determined from the integrated intensity of a single line can be more than an order of magnitude, even when the gas temperature is well known. However, if the J0?(J ? 1)0E lines, as well as the J1?(J ? 1)1A+ or A? lines are used, the relative error in the column density is no more than a factor of a few. 相似文献
194.
Chad N. Steacy Brian S. Williams Christian L. Pettersen Hilda E. Kurtz 《The Professional geographer》2016,68(1):166-173
Discourse analysis is a powerful and versatile methodological tool, informing a diverse body of critical geographic scholarship. Too often, however, discourse analysis remains unexplored, operating as a “black box,” underelaborated and hence undertheorized as to just what it offers. In this article, we articulate discourse analysis as inherently processual, by which we mean both that it should be understood as a process and that it can play an integral role throughout the research process. This article is derived from a meta-analysis of an exercise that invited early-career geographers to conduct discourse analysis on commentary centered on the 2013 U.S. federal government shutdown. The reflexive research process highlights the iterative, emergent, and dialogic properties of a processual engagement with a text. We suggest that recognizing these qualities enriches the role of both the analysis and the analyst(s) and expands the valence of discourse analysis as a productive and versatile component of critical human geography. 相似文献
195.
This study compares the residential outcomes of affluent black and affluent white households using data from the 1990 and 2000 censuses and pooled data from the 2005–2009 American Community Survey. Results indicate that affluent black households are highly segregated from their white economic peers. Furthermore, affluent black households live in neighborhoods of lower average quality compared to affluent white households. Affluent black households are least segregated from affluent white households in the South, but the greatest equality in neighborhood‐quality outcomes occurs in the West. The South, however, shows the greatest improvement in both average neighborhood quality for affluent black households and a substantial reduction in affluent black–affluent white segregation over the entire study period. The authors find that place stratification theory better describes the residential geography of affluent black households than does spatial assimilation theory. 相似文献
196.
I. K. Baldry D. W. Kurtz & T. R. Bedding 《Monthly notices of the Royal Astronomical Society》1998,300(4):L39-L42
We have detected pulsational radial velocity variations in the rapidly oscillating Ap star HR 3831 which are amplitude- and phase-modulated in the same manner as the photometric variations. In particular, the radial velocities show the same 180° phase reversal at magnetic quadrature as the photometric variations. This confirms the oblique pulsator model, and rules out the spotted pulsator model for these stars. 相似文献
197.
川滇菱形块体内部受NE向丽江 -小金河断裂的切割 ,可进一步划分为川西北次级块体和滇中次级块体等南北 2个部分 ;各次级块体东边界断裂有规律地左旋滑动、西边界断裂的右旋滑动及其滑动速率值的差异 ,反映出新生代时期各次级块体作向SE的水平滑移叠加绕垂直轴顺时针转动的复合运动。其中 ,川西北次级块体SE向的水平滑移速率 5mm/a ,顺时针转动角速度 1 4°/Ma ;滇中次级块体SE向的水平滑移速率 3 5mm/a ,顺时针转动角速度约 1 5°/Ma。在滇中次级块体内部姚安、大姚、永仁、昆明北马街等地采集到约 90个古新世地层的定向样品 ,通过交变退磁和热退磁获得了它们各自的剩磁矢量 (实验磁偏角和磁倾角 ) ,由实测磁偏角与期望磁偏角相比可知川滇地区滇中次级块体中新世早期以来的顺时针转动累积量可达 30°~ 4 8°。次级块体的整体转动与块边活动断裂的左旋滑动符合左旋走滑断裂作用区块体作顺时针转动的运动学模式 相似文献
198.
The Monitoring Network of the Vancouver 2010 Olympics 总被引:1,自引:0,他引:1
Paul Joe Bill Scott Chris Doyle George Isaac Ismail Gultepe Douglas Forsyth Stewart Cober Edwin Campos Ivan Heckman Norman Donaldson David Hudak Roy Rasmussen Paul Kucera Ron Stewart Julie M. Thériault Teresa Fisico Kristen L. Rasmussen Hannah Carmichael Alex Laplante Monika Bailey Faisal Boudala 《Pure and Applied Geophysics》2014,171(1-2):25-58
199.
Radar Detection of Near-Earth Asteroids 2062 Aten, 2101 Adonis, 3103 Eger, 4544 Xanthus, and 1992 QN
Lance A.M. Benner Steven J. Ostro Jon D. Giorgini Raymond F. Jurgens David L. Mitchell Randy Rose Keith D. Rosema Martin A. Slade Ron Winkler Donald K. Yeomans Donald B. Campbell John F. Chandler Irwin I. Shapiro 《Icarus》1997,130(2):296-312
We describe Doppler-only radar observations of near-Earth asteroids 2062 Aten, 2101 Adonis, 3103 Eger, 4544 Xanthus, and 1992 QN that were obtained at Arecibo and Goldstone between 1984 and 1996. Estimates of the echo spectral bandwidths, radar cross sections, and circular polarization ratios of these objects constrain their pole-on breadths, radar albedos, surface roughnesses, taxonomic classes, rotation periods, and pole directions. Aten's bandwidth is consistent with its radiometrically determined diameter of 0.9 km. Adonis has a rotation periodP≤ 11 h and an effective diameter (the diameter of a sphere with the same projected area as the asteroid) between 0.3 and 0.8 km. The radar properties of Adonis suggest it is not a member of taxonomic classes C or M. The effective diameter of Xanthus is between 0.4 and 2.2 km with a rotation periodP≤ 20 h. Echoes from 1992 QN constrain the asteroid's pole-on breadth to be ≥0.6 km and probably exclude it from the C and M taxonomic classes. The strongest Eger echoes are asymmetric with bandwidths that set lower bounds of 1.5 and 2.3 km on the minimum and maximum breadths of the asteroid's pole-on silhouette. If Eger is modeled as a 1.5 × 2.3 km biaxial ellipsoid, then its effective diameter for an equatorial view is 1.5 km end-on and 1.9 km broadside or pole-on, implying a geometric albedo smaller than published values but still consistent with a classification as an E-type object. The near-unity circular polarization ratios of Adonis, Eger, and 1992 QN are among the highest values measured for any asteroid or comet and suggest extreme near-surface roughness at centimeter to meter scales. 相似文献
200.
Seismic reliability assessment of lifeline networks using clustering‐based multi‐scale approach
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Seismic reliability assessment of lifeline networks gives rise to various technical challenges, which are mostly caused by a large number of network components, complex network topology, and statistical dependence between component failures. For effective risk assessment and probabilistic inference based on post‐hazard observations, various non‐simulation‐based algorithms have been developed, including the selective recursive decomposition algorithm (S‐RDA). To facilitate the application of such an algorithm to large networks, a new multi‐scale approach is developed in this paper. Using spectral clustering algorithms, a network is first divided into an adequate number of clusters such that the number of inter‐cluster links is minimized while the number of the nodes in each cluster remains reasonably large. The connectivity around the identified clusters is represented by super‐links. The reduced size of the simplified network enables the S‐RDA algorithm to perform the network risk assessment efficiently. When the simplified network is still large even after a clustering, additional levels of clustering can be introduced to have a hierarchical modeling structure. The efficiency and effectiveness of the proposed multi‐scale approach are demonstrated successfully by numerical examples of a hypothetical network, a gas transmission pipeline network, and a water transmission network. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献